We say that we are the smartest species in the planet. But, we have declared it ourselves. There’s no say in this for a dolphin or any other animal. Now, we are declaring phones as smart phones, cities as smart cities, card as smart card etc. Well, if you want to be so casual with the words, you know what? We should start calling random things smart. Like materials. Yeah! Smart Materials! Oh wait… I just googled. There are smart materials.
Fig. 1. smart material
Smart Materials. Are they though? Let’s find out!!
We are smart because we react to external stimuli (cause) with intelligence. If the temperature increases, we go into the shade. But wait. A frog doesn’t roll like that. It changes its temperature instead.
Fig 2. Meme
This of course is an inefficient system due to lack of homeostasis for the discussion of which I have a different post in mind.
Anyways, as we were, in the winter season, we wear thick clothes. We try to react to stimulus in favor of us. In case of cold, we don’t directly jump in the fire. That means, we react to stimulus in a controlled fashion. You may agree with me as long as we are talking about living things. But how can a non-living thing be smart?
There are some materials which change their inherent properties on application of external stimulus in a controlled fashion. Deja vu? These are called smart materials. The external stimulus can be temperature, pressure, electric field, magnetic field, deformation etc. The reaction can be voltage, deformation etc. Lead zirconium Titanate is a material which when subjected to pressure, produces voltage [1]. Those materials which produce voltage when pressure is applied are called Piezoelectric materials. In these materials, the structure changes when voltage is applied. Magneto rheological Fluid (MRF) is a Smart fluid whose viscosity can be varied by application of magnetic field [2]. Water flows easily, so it is less viscous. But, honey doesn’t flow easily, so it is more viscous. Viscosity is like friction in fluid. Since, the viscosity changes with magnetic field, it can be used in gun recoil, clutch brakes etc.
Fig 3. MR fluids
You now know some smart materials and their applications. Now, I would like to write about classification of smart materials. The classification is based upon the input stimuli and the physical parameter of the reaction of the material.
| Smart Material | Stimuli | Reaction |
|---|---|---|
| Piezoelectric | Pressure | Voltage |
| Magnetostrictive | Magnet | Deformation |
| Piezoelectric | Pressure | Voltage |
| Halochromic | Acid | Color |
| Photomechanical | Light | Deformation |
| Thermoelectric | Temperature | Electricity |
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